core-js/tests/unit-global/es.string.italics.js

QUnit.test('String#italics', assert => {
  const { italics } = String.prototype;
  assert.isFunction(italics);
  assert.arity(italics, 0);
  assert.name(italics, 'italics');
  assert.looksNative(italics);
  assert.nonEnumerable(String.prototype, 'italics');
  assert.same('a'.italics(), '<i>a</i>', 'lower case');

  if (typeof Symbol == 'function' && !Symbol.sham) {
    assert.throws(() => italics.call(Symbol('italics test')), 'throws on symbol context');
  }
});